The present invention relates to a method for controlling a management computer which can calculate an allowance for detecting fluctuations in a load on a server in accordance with the capabilities of the server and processing contents using an index value which permits a rapid detection of such fluctuations in the load, and a method for controlling a server to detect fluctuations in a load thereon using the index value and allowance.
In recent years, the performance of computers has been rapidly improved by virtue of the advancement of information technologies. In addition, the widespread proliferation has also been found in a form of utilizing a plurality of computers to act as servers for providing information processing services. Further, in this form of utilization, a variety of techniques have been developed for distributing loads on the respective servers (see, for example, JP-A-2001-216282).
However, there are some situations in which it is difficult to predict fluctuations in load beforehand, for example, when information processing services are provided in response to processing requests from clients which are connected through the Internet. In such situations, a sudden increase in load and the like, if any, would be desirably detected without delay such that appropriate actions can be taken therefor.
Generally, a load on a server is often indexed by a CPU (Central Processing Unit) utilization factor. However, since the CPU utilization factor can largely vary in response to even a small fluctuation on load, the CPU utilization factor should be smoothed by taking an average value over a predetermined period, and the like. Therefore, when the CPU utilization factor is relied on to indicate a load, actual sudden fluctuations on load, if any, could not be immediately detected, possibly resulting in difficulties in taking rapid actions to the fluctuations in load.
In an alternative, the number of processing requests received from clients can also be used as the index of a load on a server. In this event, an increase in the load can be immediately detected at the time the number of processing requests exceeds an allowance. However, a load on a server varies depending on the contents of processing requests and the capability of the server even if the same number of processing requests are sent from clients, so that the number of processing requests received from clients cannot be always said to reflect the load on the server.